SUNDIVING COMET: During the late hours of July 5th, an unnamed icy comet from the outer solar system dove into the sun and disintegrated. Click on the arrow to witness the death plunge recorded by coronagraphs onboard the Solar and Heliospheric Observatory (SOHO):

Over the years, SOHO has witnessed many sungrazing comets. According to SOHO Project Scientist Bernhard Fleck, "this is one of the brightest sungrazers SOHO has recorded, similar to the Christmas comet of 1996."

The comet was probably a member of the Kreutz sungrazer family. Named after a 19th century German astronomer who studied them in detail, Kreutz sungrazers are fragments from the breakup of a single giant comet around a thousand years ago, probably the Great Comet of 1106. Several of these fragments pass by the sun and disintegrate every day. Most are too small to see but occasionally a big fragment like this one attracts attention.

Although the comet has disintegrated, we may be seeing more of it in the days ahead as additional movies from other solar observatories come to light. Stay tuned.

ELECTRIC BLUE CLOUDS: Noctilucent clouds at sunset are supposed to appear in the west. That's where geometry favors their illumination. On July 5th, however, P-M Hedén of Vallentuna, Sweden, found them in other parts of the sky:

"Who says that you only can see noctilucent clouds in the west after sunset?" he asks. "Tonight I enjoyed NLCs in the south! If ordinary tropospheric clouds hadn't gotten in the way, I probably would had witnessed an all-sky display."

Indeed, NLCs seem to be spreading beyond their usual domain. Once confined to polar regions, the mysterious clouds have been migrating toward the equator. Recent displays have reached points as far south as Oregon, Colorado and even Kansas. Some researchers think this is a sign of climate change, but their conclusions are controversial. Whatever the reason, the clouds are becoming more widespread and easier to spot. Sky watchers everywhere are encouraged to be alert for electric blue just after sunset. Observing tips may be found in the 2011 NLC gallery.

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.